This application claims the priority of Korean Patent Application No. 2002-12155, filed on Mar. 7, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a method for obtaining information on position, orientation and direction of motion of a predetermined object by analyzing video data from a camera pointing at the object and a device for tracking the same, and more particularly, to a device for outputting an image corresponding to the field of view of a user by tracking the motion, i.e., position, orientation and direction of motion of a Head Mounted Display (HMD).
2. Description of the Related Art
A Head Mounted Display is a device worn on the head by a user for displaying an image near the user's eye(s). It is noted that the HMD requires a device for detecting information on position, orientation and direction of motion of the head, in order to be utilized in an application where an interaction with the user's motions is required, such as a virtual reality environment.
The level of detecting information about a user varies depending on the purpose of the application for example, from a level of inputting an image by operating one or more buttons such as a mouse or a joystick to a level of using articulation angles of the user's body. A detecting device of the lowest level is a device for tracking the position and orientation of the head of a user and adds motion tracking functionality to an image displayed by an HMD.
Recently, a widely used device for tracking the head of a user employs a gyroscope attached to the HMD, as disclosed in U.S. Pat. No. 6,162,191. The device has limits in that it can detect the orientation but not the position of the user due to the characteristics of the gyroscope. In addition, the HMD is heavy because the gyroscope is attached thereto the HMD and the speed of detecting motions of the user is low.
Another device for tracking the head of a user uses a magnetic sensor as disclosed in U.S. Pat. No. 3,983,474. The magnetic sensor can precisely detect motions of the head of the user but has limits in that the HMD is heavy because the magnetic sensor is attached to the HMD just like the case of attaching a gyroscope to a HMD. In addition, the device using the magnetic sensor can distort measurements if a metallic material is near the user.
Still another device for tracking the head of a user uses a computer vision method. U.S. Pat. Nos. 5,742,263 and 5,856,844 disclose methods for detecting the location and orientation of a user by attaching a camera to an HMD, markers to a wall where camera light hits and recognizing the positions of the markers. However the device based on these methods also has its limits in that the HMD is heavy due to the camera and light source attached thereto, and it cannot perform in other places except specifically designed places due to the use of markers.